The invention relates generally to a positioning technique in which a target object's location is estimated on the basis of observations of one or more physical quantities, such as RF signal parameter values in an environment, such as a radio communication network. The target object is an electronic device capable of making observations of the one or more physical quantities. It may be a general purpose computer or other communication device, or it may be a dedicated positioning device, colloquially referred to as a “tag”. Examples of such positioning techniques are disclosed in U.S. Pat. No. 6,393,294 and PCT publication WO2004/102936.
A feature common to the prior art techniques is a database which is based on expected signal parameter values at several locations, called sample points in the above-referenced PCT publication as well as in this document. The database contains, for each of several sample points, expected RF signal parameter values for each of the radio transmitters (also called base stations or access points) detectable in the sample point. The expected signal parameter values can be obtained by actual measurements, propagation simulations, interpolations or any combination of such techniques. As non-restricting examples, the signal parameter can be RF signal strength, phase, bit error rate/ratio, or the like. The general operating principle of the prior art positioning techniques is such that the target object makes RF signal parameter observations in the wireless communication environment, and the target object's position is estimated based on the RF signal parameter observations and the database of expected RF signal parameter values.
A problem with the prior art techniques is the high computational load required to position the target object.